Hydroxy amides from alkenes

Carbon-Oxygen Bond Formation. CAN is an efficient reagent for the conversion of epoxides into /3-nitrato alcohols. 1,2-cA-Diols can be prepared from alkenes by reaction with CAN/I2 followed by hydrolysis with KOH. Of particular interest is the high-yield synthesis of various a-hydroxy ketones and a-amino ketones from oxiranes and aziridines, respectively. The reactions are operated under mild conditions with the use of NBS and a catalytic amount of CAN as the reagents (eq 25). In another case, N-(silylmethyl)amides can be converted to A-(methoxymethyl)amides by CAN in methanol (eq 26). This chemistry has found application in the removal of electroauxiliaries from peptide substrates. Other CAN-mediated C-0 bondforming reactions include the oxidative rearrangement of aryl cyclobutanes and oxetanes, the conversion of allylic and tertiary benzylic alcohols into their corresponding ethers, and the alkoxylation of cephem sulfoxides at the position a to the ester moiety. 

A useful application of this reaction to a cyclic alkene 2 constitutes the key step in the total synthesis of thromboxane B216. Starting from methyl a-D-glucopyranoside (1), 3,6-dihydro-2-hydroxymethyT6-methoxy-ATV-dimethyl-2/y-pyran-3-acetamide (2) is obtained pure in six steps. Treatment of the amide with 3 equivalents of iodine in tetrahydrofuran/water at 0 °C for 1 hour gives the iodolactone 3 in 80% yield. Deiodination with tributyltin hydride quantitatively affords the hydroxy lactone 4. 

The stereospecific conversion of cyclohexene into the corresponding amido selenide 54 is illustrated in Scheme 8. These amidoselenenylation reactions are commonly employed for the preparation of allylic and saturated amides by oxidative or reductive deselenenylation. Propionitrile, butyronitrile, benzonitrile and ethyl cyanoacetate may be used in place of acetonitrile. Styrene gave poor results and other electron-rich olefins such as 1-methylcyclohexene or 2,3-di-methylbut-2-ene did not give the amidoselenenylation products. The reaction can also be effected starting from the hydroxy- or methoxyselenenylation products of alkenes, in the presence of water and trifluoromethanesulfonic acid in this case the nitriles are used in stoichiometric amounts [48c]. This methodology was employed to prepare the amidoselenenylation products of styrene, 55, and of electron-rich olefins. It was necessary, however, to replace the phenyl-... 

Starting from a vinyl-substimted resin, hydroboration with 9-BBN yields a homobenzylb-orane (Scheme 9). This intermediate can be coupled with various functionalized aryl iodides as well as vinyl and alkyl iodides giving rise to resins with amide, ester, or protected hydroxy functionaUties.t Similarly, bromostyrene could be coupled with functionalized boranes for the attachment of preformed handles, for example, for the construction of the silicon traceless linker.t i The carbometaUation of certain alkenes such as tropanes and the subsequent treatment with aryl boronic acid gives rise to two new C—C bonds (Scheme 10). 

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